I've just now done exactly this. Model something (not an apple) not because I want to print it, but because I need to import it into CAD to check clearances etc. around it. I can abolsutely imagine modelling different sized apples if I was building an apple sorting machine.

CAD is a 3D modeling tool.

its not the only one, and other tools are better suited for something like an apple. you can still post-process it to get it right sized for a printer